Transcript MOTION
MOTION Lesson 1: What Factors Affect Motion? Lesson 2: What Are the Laws of Motion? Lesson 1: What Factors Affect Motion? How can you tell is something is moving? You must compare it to something the is standing still. This is called a frame of reference. You look at both objects inside a “frame.” Lesson 1 How can you define motion? An object is in motion when it changes position. Position is an object’s location in space. We use words like east, behind, left, right, and above to describe motion. Lesson 1 Forces can make objects change position. All forces are pushes or pulls. Gravity is a force that pulls objects toward each other. The pull of the Earth’s gravity keeps your chair on the floor. Lesson 1 Friction is a force that opposes motion. Is slows objects down and prevents them from motion. The smoother the surface is between the two objects, the less friction there is. Not enough friction here. Too smooth of a surface. Lesson 1 Forces work together to affect the way an object moves. An airplane in flight is pulled to the ground by gravity. But a force called lift pushes it up. Drag from the air slows the plane. But thrust from the engines pushes the plane forward. Lesson 1 Some things move fast, some things move slow. How can you describe how fast something is moving? The measurement is called speed. Speed is the distance an objects travels in a certain amount of time. “Thirty miles per hour” is an example of speed. Lesson 1 Sometimes you also need to know the direction an object is going. Velocity measures an object’s speed in a certain direction. One car’s velocity may be 50 miles per hour east. Another car’s velocity may be 50 miles per hour west. The two cars have the same speed, but different velocities. Lesson 1 Acceleration is the rate at which velocity changes. Some car advertisements talk about acceleration. The ad might say, “Zero to sixty in five seconds.” The advertisement is talking about acceleration. Lesson 1 Momentum describes how easy or hard it is to stop a moving object. Momentum depends on how much mass the object has. It also depends on the object’s velocity. The more momentum an object has, the harder it will be to stop that object with a force. Lesson 2: What Are the Laws of Motion? Isaac Newton described how things move using three Laws of Motion. Law ONE: Inertia Law TWO: Acceleration depends on force/mass. Law THREE: For every forceful action, there is an equal and opposite reaction. Lesson 2 Law One: Moving objects tend to keep moving. Objects that are not moving, tend to stay still. This is inertia. For example: If you kick a ball, the ball will move. Kicking the ball overcomes the inertia that keeps the ball at rest. Lesson 2 Law TWO: If you kick a ball gently, it will move slowly. If you kick a ball hard, it will move faster. Newton’s 2nd law says than an object’s acceleration depends on the force you apply to it. The more force you apply, the greater the acceleration. Lesson 2 Law THREE: The third law says that every action force will have an equal and opposite reaction force. When you push a heavy box, you apply an action force. The box pushes back with a reaction force. Lesson 2 You have probably seen pictures of astronauts floating in their space shuttle. It looks as though there is no gravity in space, but this is not true. There is gravity, but in space, gravity is balanced by inertia. The space shuttle moves fast enough so gravity does not make it fall to Earth.